Bump shoulda-matchers from 5.1.0 to 6.4.0

Bumps [shoulda-matchers](https://github.com/thoughtbot/shoulda-matchers) from 5.1.0 to 6.4.0.
- [Release notes](https://github.com/thoughtbot/shoulda-matchers/releases)
- [Changelog](https://github.com/thoughtbot/shoulda-matchers/blob/main/CHANGELOG.md)
- [Commits](thoughtbot/shoulda-matchers@v5.1.0...v6.4.0)

---
updated-dependencies:
- dependency-name: shoulda-matchers
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -317,7 +317,7 @@ GEM
       rubocop (~> 1.61)
     ruby-progressbar (1.13.0)
     securerandom (0.3.1)
-    shoulda-matchers (5.1.0)
+    shoulda-matchers (6.4.0)
       activesupport (>= 5.2.0)
     sprockets (4.2.1)
       concurrent-ruby (~> 1.0)